This project investigates the mechanisms and evolution of social behavior and communication by adopting a within-species comparative approach to examine the neurobiology and behavior of social communication and mate choice of populations in different habitats. The cricket frog, Acris crepitans, will serve as the model system for this investigation, as a substantial body of work on geographic variation in communication signals and auditory system tuning, and their determination of mate choice behavior exists from work leading up to this proposal. This is an interdisciplinary project divided into three interrelated parts comparing two Texas populations of Acris crepitans, one occupying open grassland habitat typical of central Texas. First, the environmental acoustics of the habitats will be described. Sources and levels of environmental noise that could potentially interfere with this species' social communication will be identified by computer analysis of recordings made at natural breeding sites. Second, the sensitivity of the auditory system to the signal, the coding of signal intensity, and the ability of the auditory system to detect signals against background noise and encode their temporal characteristics will be examined via single unit neurophysiological studies of auditory nerve fibers. Third, two-choice phototaxis behavioral tests will examine females' abilities to detect calls in noise and their preferences for attenuated and degraded calls. Between-population comparisons at each stage will indicate how the habitats differ in their effects on acoustic signals; how the communication systems's signal (the call), receiver (the auditory), or both change in different habitats to mitigate these effects; and how the signal-receiver interactions influence behavioral mate choice. Synthesis of information across stages within populations will indicate whether habitat acoustics present a significant challenge, and hence selective force, for social communication given the neural and behavioral abilities of the auditory system, and will illuminate how capabilities, constraints, and biases in sensory systems influence social behavior.